Glow plug connector



March 1969 JUMPEI KATO GLOW PLUG CONNECTOR Filed Sept. 28, 1967 ATTORNEYS,

United States Patent 3,435,404 GLOW PLUG CONNECTOR Jumpei Kato, Toyonaka, Japan, assignor to Royal Prod! ucts Incorporated, Denver, (3010., a corporation of Colorado Filed Sept. 28, 1967, Ser. No. 671,22 Int. Cl. Hillr 13/44, 13/50; F02b 43/08 U.S. Cl. 339-26 6 Claims ABSTRACT OF THE DISCLOSURE A glow plug connector removably mounted in a model airplane engine or the like having a spring pressed movable contact for engaging the central terminal of the glow plug and a hexagonal leaf spring arrangement for gripping the hex body of the glow plug, so that the connector may be merely snapped onto or oil? the glow plug.

This invention relates to glow plug connectors, and more particularly to a device for connecting the glow plug of a model airplane engine to a battery, in order to start the engine.

Model airplane engines are started by a glow plug which extends into the usual one cylinder of the engine and is provided with a filament for igniting the fuel. To start the engine, the glow plug filament is connected across the battery, the current from which heats the filament of the glow plug and which heated filament ignites the compressed gas vapors within the cylinder of the engine. Once the engine has started, the glow plug may be disconnected from the battery, since the heat of the engine is sufiicient to continue the ignition of the compressed gasoline vapors in the cylinder, thereby continuing the operation of the engine.

In order to supply a current to the glow plug to secure initial heating of the glow plug filament, the glow plug terminal is insulated and normally extends from the glow plug outwardly from the main glow plug body. The circuit to the glow plug is normally completed through the body of the glow plug, which is threaded into the cylinder. Since the current to the glow plug filament is discontinued once the engine has started, a glow plug connector should be readily connected and disconnected, without any undue motions or complications.

Previous glow plug connectors have comprised a pair of alligatortype clips, each connected by a wire to one side of a dry cell battery. One clip is attached to the terminal and the other clip is attached to the main body of the glow plug or the engine cylinder, but these clips must be snapped onto and unsnapped from the terminal and body or cylinder, respectively, which requires two connections and two disconnections. The connecting and disconnecting motion for the insulated terminal is normally axial thereto, while the connection and disconnection to the glow plug body or cylinder is normally transverse to the axis thereof, thereby complicating the motions. Such alligator clips have also been combined into a single type of clip having one prong insertable between a pair of cooling fins of the cylinder, which are electrically connected to the glow plug body, and the other prong engageable with the outer end of the insulated terminal. With a single clip, faster connections and disconnections can be made than with a pair of clips, but even the single clip involves, first, the movement of the two prongs, through rearwardly extending handles connected to the same against the pressure of a spring, to release the clamping action of the clip, followed by a removal motion of the clip. In addition, when attaching such a dual alligator clip, as it may be termed, care must ice be taken in order to insert properly one of the prongs between two of the cylinder fins.

Among the objects of this invention are to provide a novel glow plug connector; to provide such a glow plug connector which can be readily snapped onto or off a glow plug; to provide such a glow plug connector in which the mere snapping of the connector on or oil the glow plug body, in an axial direction, will automatically produce contact or disconnection, respectively, with the glow plug terminal; to provide such a glow plug connector which is efi'icient and eifective in use; and to provide such a glow plug connector which may be readily manufactured.

Additional objects and the novel features of this invention will become apparent from the description which follows, taken in connection with the accompanying drawings, in which:

FIG. 1 is a side elevation of a glow plug connector of this invention, mounted on a model airplane engine;

FIG. 2 is an enlarged longitudinal section, taken along line 2-2 of FIG. 1, showing the connector mounted on the glow plug;

FIG. 3 is an enlarged bottom view of the connector;

FIG. 4 is an enlarged side elevation, partly broken away and in section, transverse to the section of FIG. 2, showing the connector prior to mounting on or after removal from the glow plug;

FIG. 5 is a transverse section, taken along line 5-5 of FIG. 4; and

FIG. 6 is a fragmentary, slightly oblique section, on a further enlarged scale, taken along line 6-6 of FIG. 2.

As illustrated in FIG. 1, a glow plug connector C of this invention may be connected to and disconnected from a glow plug G of FIG. 2, which is mounted in a cylinder 10 of a model airplane engine E, the cylinder 10 having conventional cooling fins 11. The glow plug G has a hex head 15 and a threaded base 16, within which the conventional filament (not shown) is installed, and which is threaded into an appropriate hole in the outer end of cylinder 10. One end of the filament is conventionally connected to the base 16 and the other end to a terminal 17, which is insulated from the remainder of the glow plug by insulation 18 which also extends through the head 15 around a conventional wire which connects the filament with terminal 17.

In accordance with this invention, the glow plug connector C is adapted to be snapped onto and oif the head 15 of the glow plug G, through engagement of a series of spring fingers 20 with the sides of hex head 15. As in FIGS. 3 and 5, the spring fingers 20 may be dihedral in form, separated by slots 21 and having outturned lower ends 22, which facilitate snapping the spring fingers onto the hex head 15. The upper end 23 of each spring finger is preferably arcuate, so as to fit inside a cylindrical sleeve 24, as of aluminum, whose upper end may be thicker, as shown, to resist the stresses imposed by clamping the upper ends of the spring fingers.

When the connector is snapped onto the glow plug in an axial direction, a contact 25, conveniently having a conical recess 26 on the underside, as in FIG. 2, automatically engages terminal 17, which is conveniently spherical or rounded. For this purpose, contact 25 is mounted on the lower end of a rod 27 slidable in a bushing 28 and is pressed downwardly by a coil spring 29 surrounding rod 27, which permits contact 25 to be pushed upwardly within the fingers 20. When the glow plug connector C is snapped onto the glow plug G, as described above, current is supplied to the filament within the glow plug through a pair of insulated wires 30 and 31, each having a connection clip 32 at its outer end, for electrical attachment to opposite battery terminals. These terminals need not be that of a single battery, but may be terminals provided by two or more batteries connected in series, in a conventional manner. The insulation for wires 30 and 31 may be molded together, with the insulation for the wires being separated only at the ends, as shown.

In further accordance with this invention, the connection of wire 30 with one or more of the spring fingers 20, as well as the connection of wire 31 with the contact through slidable rod 27, is electrically insulated by an outer housing H and an inner plug P, each formed of insulating material, for example 'a suitable plastic, such as nylon. Housing H is hollow and generally cylindrical, having an integral spout 33, through which wires and 31 extend and which assists in preventing the wires from being broken, particularly when the connector is disconnected from the glow plug. The housing H is further provided with a closed upper end 34 and an exterior, tapering lower portion 35 which surrounds cylindrical sleeve 24.

The central plug P is generally cylindrical, being provided with an upper flange 38 against the underside of which spring fingers 20 and sleeve 24 abut, as well as with a central bore through which bushing 28 extends. A flange 39 at the upper end of bushing 28 is adapted to clamp a connection terminal 40 against the top of plug P. For connection to wire 31, as by soldering, terminal 40 is provided with an upstanding nib enclosed within insulation 41, which is molded around the connection at an appropriate time. Wire 30 is connected, as by soldering, to a prong 42 upstanding from one of the spring fingers 20, as in FIG. 6. For convenience, each of the spring fingers 20 may be provided with a similar prong 42, but only one need be connected to wire 30, with insulation 43 covering the connection in a manner similar to insulation 41. The lower end of coil spring 29 bears against a disc 45 which is mounted atop contact 25 and is formed of insulating material to space contact 25 from spring fingers 20, as the contact is moved upwardly and downwardly in the space within the spring fingers. In addition, a stop 46 is mounted at the upper end of slidable rod 27, to prevent spring 29 from pulling the rod out through bushing 28. Stop 46 conveniently comprises a piece of small wire looped into a groove formed in the upper end of rod 26 and the ends of the wire twisted together.

For manufacturing purposes, bushing 28 and terminal 40 may be placed in a mold and the plastic material, such as nylon, of plug G injected into the space around the bushing. Spring fingers 20 may be inserted within sleeve 24 and rod 27, with which contact 25 may be integral and 1 on which disc 45 and spring 29 have been mounted, slipped upwardly through bushing 28 and stop 46 affixed to the upper end of rod 27. Spring fingers 20 may then be placed within sleeve 24 and slipped onto plug P. Before atttachment of wires 30 and 31 to prong 42 and terminal 40, respectively, one end of the two insulated wires is inserted, from the outside, through spout 33 and threaded through housing H, until a suflicient length of wire is exposed. After attachment of the ends of the wires to a prong 42 and terminal 40, insulation 41 and 43 is placed around the respective connections. Then, the wires are pulled in the opposite direction through spout 33 and the assembly, including plug P and sleeve 24, inserted into the lower end of housing H. Conveniently, the fit of plug P and sleeve 24 requires pressure for insertion, so as to slightly expand the bore end of housing H and insure that it will clamp tightly the sleeve and plug.

As will be evident, a glow plug connector has been provided which fulfills to a marked degree the requirements and objects hereinbefore set forth. For example, the glow plug connector of this invention may be readily snapped onto or off of a glow plug in a single, simple motion. The snapping on motion insures that the contact 25 will engage the glow plug terminal 17. As will be evident, the contact area between slidable rod 27 and bushing 28 is considerable, so that an adequate flow of electrical current to contact 25 and terminal 17 is assured. Also, only one spring finger 20 need engage hex head 15 of the glow plug to insure an adequate connection, although the engagement of the upper end of each of the spring fingers 20 with sleeve 24 also provides an opportunity for each spring finger to form an electrical connection with the hex head 15. Housing H is easily gripped to snap the connector onto or off the glow plug, while spout 33, as indicated, protects the wires during attachment and removal of the connector. Although a number of parts are involved, the housing H and plug P may be formed readily by molding, while the other parts may be formed readily by stamping or similar machine operations. Also, the assembly of the parts is relatively simple, jigs desirable to facilitate assembly being well within the cognizance of those skilled in the art.

Although a preferred embodiment has been illustrated and described, it will be understood that other embodiments may exist and that various changes may be made, all without departing from the spirit and scope of this invention.

What is claimed is:

.1. A glow plug connector removably attachable to a glow plug mounted in a model airplane engine or the like, said glow plug having a head extending from the engine and a central terminal spaced outwardly and in an axial direction from the head, said connector comprising:

(a) a generally cylindrical housing of insulating material and open at one end;

(b) gripping means formed as an axially elongated, circumferential array of surfaces extending from the open end of the housing and the extended end of which is adapted to engage the glow plug head in axial alignment therewith to make an electrical connection thereto;

(0) insulated bushing means within the housing adjacent the inner end of the array of surfaces and having an axially centered passageway therethrough;

(d) contact means including a rod mounted in the bushing passageway and extending axially within the gripping means, said rod having a contact at its extended end disposed adjacent to the extended end of the gripping means and said rod being axially shiftable to cause said contact to engage the glow plug terminal when the gripping means is engaged with the head;

(e) a spring about the rod adapted to resiliently urge said contact against the aforesaid terminal; and

(f) insulation means about the rod adjacent said contact means and engageable with said gripping means to prevent the contact from touching the gripping means.

2. In a glow plug connector defined in claim 1, wherein:

said insulation means comprises a disc surrounding said rod adjacent to said contact.

3. The glow plug connector defined in claim 1, wherein:

said glow plug head is a multiple sided member; and

said surfaces comprise multiple sided flats for engaging the sides of the head.

4. The glow plug connector defined in claim 1, wherein:

said spring is disposed about said rod between said bushing means and said insulation means;

a stop at the inward end of the rod is adapted to limit its outward extension; and

said bushing means includes a plug of insulating material closing the inner end of said gripping means, a metallic sleeve extending through said plug, and an electrical connector flange on said sleeve and extending inwardly therefrom.

5. The glow plug connector defined in claim 1, wherein:

said gripping means comprises a series of longitudinally extending, circumferentially spaced resilient fingers whose inward ends surround said bushing means, with at least one finger having an inwardly extended prong,

for connection with an electrical wire; and

said housing extends beyond said bushing means, to provide a closed space beyond said bushing means.

6. The glow plug connector defined in claim 5, wherein:

said glow plug head is hexagonal;

said insulated bushing means is cylindrical;

said gripping means comprises three spring fingers, each having a lower portion formed as a dihedral angle providing a pair of flat surfaces for engaging two sides of said head and an arcuate portion to fit around said insulating bushing means;

an annular sleeve surrounds said fingers and grips the upper portions thereof against said bushing means; and

said housing extends along said sleeve to a position beyond the bushing means and is provided with a closed end and a lateral spout through which connecting wire extend.

6 References Cited UNITED STATES PATENTS MARVIN A. CHAMPION, Primary Examiner.

JOHN R. MOSES, Assistant Examiner.

U.S. Cl. X.R. 123-3; 339182 

